One example of an infrared oven heretofore used in the art is a continuous infrared oven available from Unitherm Food Systems, Inc. for removing purge material and free moisture from the surfaces of bag-cooked turkey breasts or hams prior to applying liquid smoke products or other browning liquids thereto. Another example of an infrared oven known in the art is a continuous infrared oven available from Unitherm Food Systems, Inc. for pasteurizing the surfaces of precooked food products prior to packaging.
The continuous infrared ovens used in these applications typically comprise: an elongate insulated housing having inverted-U-shaped inlet and outlet openings; a conveyor (typically a stainless steel wire belt) having an upper carrying run extending longitudinally through the housing; and a series of inverted-U-shaped electrical infrared elements extending laterally over the conveyor carrying run.
The inverted-U-shaped infrared elements used in these systems have consisted of: a source terminal located on one lateral side of the conveyor; a return terminal located on the other lateral side of the conveyor; and an inverted-U-shaped element segment extending laterally over the conveyor from the source terminal to the return terminal. The inverted-U-shaped elements thus desirably surround and directly irradiate the upper surface and both side surfaces of the products and can be conveniently sized to allow even large products such as whole turkeys and hams to be conveyed through the oven without difficulty.
The Unitherm continuous infrared ovens used for surface pasteurization have also included a series of lower infrared elements extending laterally beneath the wire conveyor for directly irradiating the bottom surfaces of the products. These lower infrared elements have consisted of: a source terminal located on one lateral side of the conveyor; a return terminal located on the other lateral side of the conveyor; and a straight or slightly arched element segment extending beneath the belt from the source terminal to the return terminal.
The Unitherm continuous infrared ovens used heretofore for surface pasteurization have been of two basic types, single lane infrared ovens and dual lane infrared ovens. The dual lane ovens have been substantially identical to the single lane ovens except that the dual lane ovens have included a pair of conveyors. The dual conveyors extend side-by-side through the oven housing such that the lateral inner side of one conveyor is adjacent to the lateral inner side of the other conveyor. The upper and lower infrared heating elements used in the dual lane ovens have also been identical to those used in the single lane ovens so that each lane includes its own individual series of upper inverted-U-shaped elements above the belt and its own series of lower elements beneath the belt. Each of the upper and lower elements has a first terminal located on the outer lateral side of the belt and a second terminal located on the inner lateral side of the belt.
A need presently exists for an improved dual lane infrared oven and for improved infrared elements which can be used therein. It has been necessary heretofore that the inner end of each of the upper and lower elements used in each lane be installed, and that the necessary leads and connections therefore be directed to and provided within, the central interior portion of the oven. Such interior connections are not readily accessible and (a) significantly increase the complexity of the dual lane oven versus a single lane oven, (b) can require the use of materials capable of withstanding higher temperatures within the central part of the oven, (c) typically require that both processing lanes be shut down when a problem in one lane occurs, and (d) can make the oven more difficult to operate, repair, and maintain.
Previous attempts to address these shortcomings have not been successful. It has been suggested, for example, that, rather than each dual lane having its own individual series of upper infrared elements, a single series of wide upper infrared elements be used such that each element extends laterally over both conveyors. The wider elements would thus extend laterally across the entire oven such that the element source terminals would be located on the outer lateral side of one of the belts and the element return terminals would be located on the outer lateral side of the other belt. Unfortunately, the use of such elements results in (a) the inner sides of the products on each belt being shadowed by the products traveling down the other belt and/or (b) the upper infrared elements being much closer to the outer side of the product than to the innerside. Thus, the use of elements of this type would result in uneven, nonuniform irradiation and in inadequate heat transfer to the inner side of the product.